1. Field of the Invention:
This invention relates to an apparatus for grouping flexible, identically shaped sheetlike objects, such as copies of newspaper or other printed matter, into sets or lots which are composed of an equal number of objects, while they are being conveyed in a row in which they overlap one another in a mutually equally spaced apart relation.
2. Description of the Prior Art:
When a multiplicity of printed and folded objects which are identical in shape are conveyed in a long and orderly row in which they overlap one another in a mutually equally spaced apart relation, they must be divided into a plurality of groups prior to their delivery to the next step of the production process. They must be grouped accurately into a plurality of sets consisting of an equal number of objects without causing any disorder in their row between one set and another, even if they may be conveyed at a high speed.
There are known a variety of apparatus for dividing such a row of mutually overlapping objects positioned in close proximity to one another. They usually include a pawl which is lowered toward a conveyor belt to hold the printed objects upstream of the pawl against movement temporarily. They are further classified into two main types by the pawl which they have, i.e., an apparatus having a pawl of the simply descending type as disclosed, for example, in Japanese Patent Publication No. 13459/1983 and an apparatus having a pawl of the type which can both descend and move along the conveyor belt as disclosed, for example, in Japanese Patent Publication No. 13443/1977.
In either event, however, it is not easy to lower the pawl to a level of height which best suits the thickness of each of various kinds of printed objects. The failure to lower the pawl to an appropriate level of height ca result in a variety of problems. If the pawl is lowered too much, it holds the rear edge portion of the last object in the row downstream of the pawl and prevents it from being conveyed. There is every likelihood that the last object may be spaced apart from the other objects of the same group by so large a distance that it cannot be clearly identified as one of the objects belonging to that group. If the pawl is, on the other hand, lowered insufficiently, it may fail to hold the first object in the row upstream thereof and be, therefore, unable to group the objects properly.
When the pawl of the simply descending type is lowered, the objects upstream of the pawl can no longer move forward, but gather behind the pawl, while losing their appropriately spaced apart overlapping relationship. This problem remains present even after the pawl has been raised. The objects which have gathered displace themselves transversely of the conveyor belt. This disorder in the row of objects has an adverse effect on any subsequent step of the production process.
These drawbacks have been overcome by the pawl of the descending and moving type. However, it is very difficult, even if not impossible, to rely upon only a single pawl for grouping a long row of closely contiguous objects conveyed in a mutually spaced apart overlapping relation. Therefore, even the latter type of pawl is not free from the problems which can arise if it is lowered too much or insufficiently.